Small Office Network Design

Many small businesses use their computer networks to organize their assets, inventory, finances, communications, customer records, and operations. The network, and the systems attached to it are important, and like any business, keeping costs under control is crucial.

Business class networks are a step up in complexity over residential networks. The requirements of any business network are more or less as follows:

Since all the requirements in some way impact the bottom line of the business, it is worth taking some time on how these requirements impact the design and what they mean.

A Reliable Network

A simple rule of thumb for reliability is, the more reliable, the more expensive. Also, there is no such thing as a 100% reliable design.

What's left is a trade-off between reliability and costs.

From a small office perspective, the ideal network sits somewhere between "It works at home" and "This has got to work".  Therefore hardware decisions should look at characteristics like warranty, peer review, environmental durability and mean time to failure. Complex features such as redundancy and remote administration may be less important, or unneeded.

If power outages are considered an inconveniance rather than a crisis, redundancy is probably not a requirement.

A Maintainable Network

Since 100% reliability is impossible, eventually maintenance will be necessary.

Either a technician will be called in to handle maintenance when it is required, or office staff will handle the situation.  Situations that resolve without the necessity for a technician are less expensive, therefore network designs where the majority of the network faults can be handled by the people onsite are preferrable.

Although maintainability is difficult to quantify, there are some characteristics of maintainable networks to take into consideration:

Consider the following circumstance with a maintainable network. A single computer on a wired network is unable to connect since the cable from the patch panel to the ethernet switch has come loose.

From glancing at a network map and looking at the connectivity lights at a centralized switch it becomes apparent that the physical connection between the switch and the computer has been broken. Reconnecting the loose patch cable will fix the problem, and was easy to spot.

The same situation with an unmaintainable network might involve tracking down the series of connections tying the computer to the network and identifying which one has become loose. This could take hours in the worst case and require disconnecting other machines in the process of trying to find the right one.

Designing for maintainability is important if avoiding disruption during service calls is important.

Although the following picture is blurry due to being taken by a camera phone it demonstrates an unmaintainable  network.

Unmaintainable Computer Network

While dealing with recurring network problems, this business owner chose to keep the current network "as-is" and run an entirely separate office network in parallel which worked properly and was understood. This was the less expensive choice since the cost of maintaining or fixing the above network was too high.

Designing for maintainability is critical to the long term costs of having a network.

Network Performance

Most small offices favour functionality over performance when it comes to their computer networks. However that doesn't mean that the topic should be ignored when considerng the design for the network.

The highest level of performance and reliability is available through the use of wired network technologies. This will remain the case for the forseeable future, however wireless technology has experienced a marked boost in performance and reliability with the advent of the 802.11n amendment to the wifi standard.

Small offices which are interested in maximizing the performance of their network should look to use gigabit wired network technologies, routed through a single gigabit ethernet switch. Additional performance can be achieved by switching the MTU (Maximum Transimission Size) of data on the network to 9k bytes up from the old standard of 1500 bytes. This is achieved by reducing the effective overhead of transmitting data on the network. Check for jumbo frame compatibility on any connected wired hardware before deploying this strategy.

A Feature Complete Network

Unless office networks are well designed, they can be difficult to upgrade. For instance, a business network which has most of its routing configuration stored in the router with no way to export the configuration to a different machine will be harder to take down and replace than a device which can export its configuration.

Sometimes a new feature is required after the network has already been built, only to discover that the current system cannot handle the new feature. One example may be dhcp static allocation, which is a feature that is not uniformly available across commodity routers. Another example is VPN support; a feature highly in demand for those on the road or with a home office trying to tie into work.

Designing a network that can accomodate future necessities can be challenging, especially when dealing with commodity hardware, however there are variety of router appliances which can make these challenges much less cumbersome. Examples of these appliances are pfSense, m0n0wall, freenas, smoothwall and others.

Determining whether router appliances are necessary is a useful exercise since it helps specify the networks feature requirements.

An Affordable Network

The cost to build, maintain, and extend a computer network is the true deciding factor for most if not all business. Commodity components may be affordable from an upfront perspective, undesirable from a reliability perspective and completely pointless from a maintenance, or feature perspective. The converse may be true of router appliance packages such as pfsense.

The costs that comprise working on a new network design are as follows:

Designing a network takes into account the logical and physical topology, the performance requirements, hardware, cable requirements (outdoor, indoor). Installation examines how long, and what will be necessary to implement the design. The maintenance cost deals with what will be involved in ensuring the network continues to function over time.

Upfront design costs can seem fairly intimidating, however it is important to consider the long term benefit of having a well designed office network. Downtime is minimized, maintenance is straightforward when necessary, the network generally performs well.

Small Office Network Design Strategies

Keeping costs in check is an important consideration when developing business networks. Small businesses by there nature do not have large amounts of resources to the devote to business infrastructure. To balance this with the necessity to actually implement a network which will meet the current and foreseeable needs is the role of the network designer.

Hardware

Some hardware components are straightforward to replace such as switches, patch cables and to a lesser extent, routers. This contrasts to in-wall cabling, keystone jacks, cable tracks and any other fixed device or installation.

It is a good practice to use high-quality components for any hard to reach parts that will need to remain functional and compatible. Using Cat6 over Cat5e cable for in-wall cable drops is a good example of this; another example is using shielded keystones rather than the unshielded alternatives. Even though a business may not initially require high-speed components, it is a useful strategy to future-proof the implementation by using materials capable handling future technologies.

Services

Keep services centralized as much as possible. Relying on user desktops to provide services to the network will eventually result in business downtime during reboots or other maintenance. Setting up a small business server which runs file-sharing, backups, CRM, financial and other business applications makes managing a network simpler.

Network related services such as local DNS, DHCP and routing can generally be provided by a single machine such as a commodity router, or routing appliance like pfSense.

Topology

Small network planning does not require much effort on the logical topology, beyond some basic analysis of which services need to be available and how they will be controlled. On the otherhand, a well executed physical topology plan is very useful since it gives a clear map of how the network works.

Plan on creating a port map which shows where each component is connected and how the connections map out to locations on the network.

Conclusion

At the end of the day, the challenge of desiging a small office network is finding that balance point between reliability, maintainability and cost. The limiting factor, as always, is the projects budget.

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